1. Field of the Invention
The present invention relates generally to a lead frame for semiconductor electronic parts, and more particularly to a lead frame in use for semiconductor electronic parts called a QFN (Quad Flatpack Non-leaded) package.
2. Description of Related Art
Conventionally, a lead frame has been formed with an island to land a semiconductor chip thereon and a plurality of leads to be connected to respective electrode pads of the semiconductor chip landed on the island via metal wires as conducting means by applying die-cutting and etching processes to a thin metal plate extending in one direction. Semiconductor electronic parts have been formed by landing the semiconductor chip on the island of the formed lead frame using a die-bonding agent, electrically connecting the given leads to the respective electrode pads of the semiconductor chip using metal wires of gold or aluminum and molding the semiconductor chip to be sealed with a molding resin, followed by cutting the leads extending from a body part formed with the molding resin at predetermined lengths in order to separate the semiconductor chip sealed with the molding resin from the lead frame.
After separation from the lead frame, the leads have been shaped as required. Besides, predetermined plated coatings have been arranged on the connections of the leads to be connected to connection terminals provided on a mounted board.
The semiconductor electronic parts produced using such lead frames include those in the form called a QFN (Quad Flatpack Non-leaded) package.
The QFN semiconductor electronic parts have involved exposing the lower faces of leads to the lower face side of the approximately rectangular body part formed with the molding resin in almost the same plane as the lower face thereof and preventing the leads from extending from the body part by cutting the leads along the outer periphery of the body part.
Thus, the product dimension of the QFN semiconductor electronic parts could be reduced in proportion as the leads did not extend from the body part, and the mounting efficiency of the mounted board could be enhanced.